1. Field of the Invention
The present invention relates to adjustable attenuation devices, and more particularly to such devices employed in digital telecommunications systems such as telephone exchange systems.
2. The Prior Art
Adjustable attenuation devices are known, as shown in British Pat. No. 1,325,193. As disclosed therein, an amplification or attenuation of a tone frequency is carried out by an amplitude multiplier unit so that a nominal loudness level of the respective tone is attained. Such a tone may be transmitted to a subsequent compander and to a parallel-to-series converter. The amplification factor of the multiplier unit is variable and controlled by an amplification control. The multiplier unit contains a very extensive conversion table, to accommodate a variety of amplitudes of the tone frequencies to be present and to allow for their output in the same form. If a less extensive conversion table is employed, only relatively few amplification factors may be provided.